For many patients using injecting devices for self-administration of medicament, there is a discomfort to handle the device, especially regarding the penetration. For many users there is a mental resistance against self-penetration. Other users also have a general fear of needles which enhances the discomfort and negative feeling of self-administration. Also, when the needle is about to slowly penetrate human skin; there is a certain start resistance that can give the user discomfort.
It is further desirable for many patients that the number of actions that the patient needs to perform in order to receive a dose of medicament is held as low as possible, on the one hand regarding handling of the device and on the other hand the functionality of the device.
One such device is disclosed in patent EP 1349590 B (SHL MEDICAL AB) 2003-10-08 describing an injector having a number of features that facilitate the handling of the injector. The penetration and injection is performed automatically by pressing a button on the upper end of the injector. When the injection is performed the injector is withdrawn whereby a needle shield extracts around the needle in a locked way. As an additional safety aspect, the activation cannot be performed unless the injector is pressed against an injection site, i.e. a two-step operation to activate the injector is required.
Another type of injecting device is shown in U.S. Pat. No. 5,478,316 (BECTON DICKINSON CO) 1995-12-26 disclosing a high degree of automatic functions. When a sleeve at the front injection end of the injector, being the needle shield, is pressed against an injection site, the sleeve is moved a certain distance into the injector. The movement enables a push button arranged about midway on the side of the injector housing to be pressed by the user. This in turn releases a constant spring means acting on a driver and rod unit in contact with a syringe assembly so that a penetration is performed. When a certain penetration depth is reached, the driver is disconnected from the rod and the rod is urged further by the spring, causing an injection of medicament into the injection site. After the injection is completed the device is withdrawn from the injection site, whereby the sleeve moves forward, covering the needle.
Another aspect of injectors is the human aspect of handling the injector regarding how it is held during operation. A general aim is to have the patient holding the injector in an ergonomic way that may permits the penetration and injection in different locations on the body, such as around the waist and also on the backside of the waist and/or in the buttocks of the patient. The patient does not see the injector at those locations and need to be able to hold the injector without having to change grip. One suitable ergonomic grip for many locations is e.g. the pen grip, whereby the user holds the injector in the front, injection area. This could be difficult when the injector has push buttons on the distal end of the injector or slide buttons on the side of the injector.